1. Field of the Invention
The present invention relates to a method for concentration and recovery of gold in a leach residue obtained by leaching copper from a gold-bearing copper sulfide mineral in a copper hydrometallurgical process for recovering copper from a copper sulfide mineral.
2. Description of the Related Art
Copper sulfide minerals used as raw materials for copper smelting contain copper-containing components such as chalcopyrite, bornite, and chalcocite, iron-containing components such as pyrite, gangue components containing silicon, calcium, etc., and noble metal components such as gold.
In a typical copper pyrometallurgical process, the copper sulfide mineral is concentrated to obtain a copper concentrate with high copper grade, and then the copper concentrate is smelted in a furnace in a smelting process. At this time, iron and sulfur are separated as a slag and a gas, and the copper concentrate is converted into blister copper. Then, the blister copper is processed into anode copper and electrolytically refined in an electrolysis process. In the electrolysis process, copper is separated from gold and other impurities, electrodeposited onto a cathode, and recovered as electrolytic copper.
Such a copper pyrometallurgical process is highly productive, but has problems that capital investment is very high, it takes much time, effort, and cost to treat generated gas and slag, and operational adjustment is difficult. For this reason, a copper hydrometallurgical process has been recently developed, which can be performed by more compact facilities than the copper pyrometallugrical process and can achieve operational adjustment with ease.
For example, Japanese Patent Kohyo No. 2004-504492 proposes a copper hydrometallurgical process including a step of subjecting a copper-containing material to pressure leaching at approximately 170 to 235° C. to obtain a leach residue and a copper-containing solution, a step of diluting the copper-containing solution with a diluent to prepare a dilute copper-containing solution, and a step of extracting copper from the dilute copper-containing solution with a solvent. According to this method, however, gold contained in the copper-containing material is dispersed throughout the leach residue obtained by pressure leaching. Therefore, it is necessary to treat the entire leach residue again to recover gold, which requires very high cost.
Japanese Patent Kohyo No. 2001-515145 proposes a process for leaching of copper from a sulfide ore, which includes oxidizing ores or concentrates under pressure in the presence of oxygen and an acidic solution containing a halide and sulfate ions to obtain a slurry, subjecting the slurry to solid-liquid separation to obtain a filtrate and a solid residue containing a basic metal sulfate, and subjecting the solid residue to leaching with an acidic sulfate solution. A leach solution is separated from the solid residue and subjected to solvent extraction to produce a metal-rich solution (pregnant liquor) and a metal-depleted raffinate (barren liquor). However, a leach residue obtained by this method is a mixture of iron oxide micro particles and sulfur micro particles, and therefore it is difficult to separate and recover gold from the leach residue.
As a method for separating iron oxide and sulfur from such a leach residue obtained by copper leaching, a method proposed in Japanese Patent Kokai No. 2002-053310 is known. This method includes subjecting a leach residue, which is obtained by subjecting a sulfur-containing material such as a zinc concentrate to leaching in a leaching step, to flotation to obtain a sulfur-rich float fraction, heating the float fraction to a temperature equal to or higher than the melting point of sulfur but lower than the boiling point of sulfur to produce sulfur vapor, and cooling a gas containing the sulfur vapor at a temperature lower than the melting point of sulfur to condense and recover sulfur. This method makes it possible to efficiently recover sulfur from a leach residue obtained by subjecting a zinc concentrate to leaching.
Japanese Patent Kokai No. 2005-042155 proposes a method for concentrating noble metals contained in a leach residue obtained by leaching copper from a copper ore or a copper mineral. According to this method, the leach residue is heated at a temperature of 550° C. of higher under a nonoxidative atmosphere to produce a calcined ore, and the calcined ore is again subjected to leaching with an acidic solution to obtain a leach residue containing sulfur and noble metals and a leach solution containing iron. However, gangue components contained in a copper mineral or a copper concentrate are often distributed in the same manner as noble metals. Therefore, in a case where a copper mineral or copper concentrate containing a large amount of gangue components is treated by this method, there is a problem that it takes much time and effort to separate noble metals from the gangue components.
As described above, in a copper hydrometallurgical process for recovering copper from a gold-bearing copper sulfide mineral, a leach residue obtained by leaching copper from the copper sulfide mineral contains gold, but it is very difficult to concentrate gold contained in the leach residue, thereby making it impossible to efficiently recover gold from the leach residue.